Allied Telesis AT-MR820TR - Manual (Page 62)

Glossary
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MEDIUM ATTACHMENT UNIT (MAU)—In a LAN, a device used in a data
station to couple the DTE to the transmission medium.
MEDIUM DEPENDENT INTERFACE (MDI)—The mechanical and
electrical interface between a hub and a transceiver (MAU). MDI-X is another
version of the interface that enables hubs to connect using different pin-outs,
thereby avoiding conflicts that occur when receiving and transmitting packets
use the same pin-out.
N-SERIES—A barrel shaped, threaded connector used on 10Base5 (thick
Ethernet) coaxial cable.
PATCH PANEL—A 10Base-T patch panel may be used between a punch-
down block and STP/UTP workstation. The patch panel generally has a female
RJ45 connector on the front for each workstation and a Telco (RJ21) connector
on the back, which is wired to a punch-down block. This provides a convenient
way for the installer or network manager to connect the hub 10Base-T ports
into the desired building locations.
POLARITY CORRECTION—Many 10Base-T STP/UTP ports have a polarity
correction function. If the STP/UTP wiring has RD- and RD+ inadvertently
crossed, the polarity correction function will sample the signal and electrically
swap the wires. If the TD- and TD+ wires are crossed, the correction would
occur at the MAU on the other end of the STP/UTP link. This occurs within a
single pair and should not be confused with the crossover cable.
PROPAGATION DELAY—The time it takes a signal to travel from the input
of a system component to the output. Usually measured in nanoseconds. IEEE
802.3 has specific propagation delay maxima for computing propagation
budgets when designing a LAN. Cable length plays a major role in propagation
delay; for example, a 50-meter (164-foot) AUI cable has a maximum allowable
propagation delay of 257 ns. The propagation delay of cable depends on the
length and velocity factor of the cable type. There are also propagation delays
associated with electronics attached to the system.
PUNCH-DOWN BLOCK—The punch-down block is the wiring panel where
the house wiring from the building’s offices terminates. This is where many
10Base-T hubs would be located. Wiring installers use a special punch-down
tool to insert the STP/UTP wire for data and voice applications.
REPEATER—A device used to extend the length, topology, or
interconnectivity of the physical medium beyond that imposed by a single
segment, up to the maximum allowable end-to-end trunk transmission line
length. Repeaters perform the basic actions of restoring signal amplitude,
waveform and timing applied to normal data and collision signals.
RJ45—This connector is a 10Base-T standard for connecting STP/UTP cabling.
SIGNAL QUALITY ERROR (SQE)—Also referred to as Collision or Collision
Presence. This occurs when two devices attempt to transmit at the same time,
which is an illegal condition. All ATI transceivers test for SQE.
MRx20TR(STP/UTP)_BookA Page 40 Thursday, April 3, 1997 5:24 PM